The present invention relates to a method for safe removal of a semiconductor IC chip or die from a circuit board comprised of a brittle material. More particularly, the invention pertains to a method for safely removing, e.g., for performing failure analysis or other type testing, a die or chip comprising a semiconductor integrated circuit device from a brittle circuit board, e.g., comprising a ceramic-based substrate, without causing breakage of the substrate or damage to very fine wires and landing pads on the ceramic substrate utilized for electrically connecting the IC chip or die to the substrate.
Electrical and electronic devices typically comprise a plurality of individual components and component devices mounted on at least one surface of a circuit board, e.g., a printed circuit board (xe2x80x9cPCBxe2x80x9d), and electrically interconnected by means of circuitry located on or beneath the surface(s) of the PCB. The PCB comprises a substrate material, typically in the form of a sheet having opposed planar surfaces on or below which the circuitry is formed and the various components and/or component devices mounted. Typical substrate materials include resins, polymers, polymer composites and laminates, resin-impregnated fiberglass, fiberglass/polymer composites and laminates, ceramics, and glass ceramics, which materials possess varying degrees of fragility and/or brittleness, with ceramic-based materials being most fragile and brittle.
It sometimes becomes necessary, e.g., for quality control, troubleshooting, failure analysis, etc., to perform electrical testing of the individual components and/or component devices, e.g., IC dies or chips, mounted on the PCB. However, accurate testing of the individual components and/or component devices is not always feasible or practicable when the components and/or component devices are electrically interconnected on the PCB substrate because of device interaction (i.e., mutual interference between devices) and the particular circuitry connecting together a plurality of components and/or component devices which can mask or altogether prevent meaningful electrical testing of a particular, e.g., suspect, component or component device. In such instances, it becomes necessary to physically remove the particular component or component device, such as an IC die or chip, from the PCB and any associated mountings, metallic housings, etc., in order to perform meaningful, accurate electrical testing and analysis. Such component removal, however, frequently is problematic in that many of the components and/or component devices are miniaturized and electrically connected to bonding pads on the PCB substrate by a plurality of very narrow diameter, fragile wires which are highly susceptible to breakage during the removal process. The problem of safe component removal, e.g., die or chip removal, is further exacerbated when the PCB substrate itself comprises a fragile and/or brittle material, such as a ceramic-based material. To date, no satisfactory technique exists which reliably provides safe removal of components such as IC dies or chips from PCB substrates comprised of fragile and/or brittle materials, notably ceramic-based substrates.
Accordingly, there exists a need for improved methodology for reliable, safe removal of components and/or component devices, such as IC dies or chips, from fragile and/or brittle PCB substrates, such as ceramic-based substrates, which methodology does not incur damage to the component or component device, the fragile/brittle PCB substrate, and the narrow diameter wire interconnections between the component or component device and the associated bonding/landing pads on the PCB substrate.
The present invention, wherein a series of cutting steps are performed for isolating and separating the portion or segment of a fragile/brittle PCB substrate having mounted thereon the subject component or component device from the balance of the PCB substrate by a process utilizing, e.g., diamond table and wire saws, effectively addresses and solves problems attendant upon the removal of components or component devices from fragile/brittle PCB substrates, while maintaining full compatibility with all aspects of electrical , etc., testing. Further, the means and methodology provided by the present invention enjoy diverse utility in the manufacture of numerous types of electrical and electronic devices.
An advantage of the present invention is an improved method for reliable, safe removal of an electrical or electronic component from a fragile and/or brittle substrate.
Another advantage of the present invention is an improved method for reliable, safe removal of a semiconductor integrated circuit (IC) device in the form of a die or chip from a brittle, ceramic-based circuit board.
Yet another advantage of the present invention is an improved method for electrically testing an electrical or electronic component or component device safely removed from a fragile and/or brittle circuit board.
Additional advantages and other features of the present invention will be set forth in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present invention. The advantages of the present invention may be realized and obtained as particularly pointed out in the appended claims.
According to one aspect of the present invention, the foregoing and other advantages are obtained in part by a method for reliable, safe removal of an electrical or electronic component or device from a fragile and/or brittle substrate comprises the sequential steps of:
(a) providing a fragile and/or brittle substrate having an electrical or electronic component or device mounted on a first portion of a planar surface thereof;
(b) cutting the substrate transversely through the thickness thereof to separate therefrom a segment comprising the first portion including the component or device and an adjoining second portion;
(c) cutting the separated segment along a plane parallel to the planar surface, the cutting extending beneath the entirety of the first portion; and
(d) cutting the substrate of the separated segment transversely through the thickness thereof to separate the first portion thereof including the component or device from the second portion.
According to a embodiments of the present invention, steps (b) and (d) comprise cutting transversely through the substrate by means of a table saw; and step (c) comprises cutting the substrate longitudinally by means of a wire saw, wherein step (c) further comprises maintaining the separated segment in a fixed position during the longitudinal cutting via a clamping device which grips the second portion thereof adjoining the first portion.
According to further embodiments of the present invention, step (a) comprises providing a substrate with a component comprising a semiconductor integrated circuit (IC) device in the form of a die or chip mounted on the first surface portion thereof, the substrate comprises a circuit board, and the IC device is electrically connected to the first portion of the circuit board substrate on the upper side thereof via a plurality of fine diameter wires extending therefrom to a plurality of bonding pads formed on the first surface portion.
According to yet further embodiments of the present invention, step (a) comprises providing a circuit board substrate comprised of a material selected from the group consisting of resins, polymers, polymer composites, polymer laminates, resin-impregnated fiberglass, fiberglass/polymer composites, fiberglass/polymer laminates, ceramics, and glass/ceramic composites.
According to particular embodiments of the present invention, step (a) comprises providing a ceramic-based circuit board substrate; step (a) further comprises providing the circuit board substrate as a laminate including a metal backing sheet bonded, e.g., adhesively bonded, to the lower side of the circuit board, or step (a) comprises increasing the rigidity of the circuit board substrate prior to performing the cutting steps (b)-(d) by bonding, e.g., adhesive bonding, a metal reinforcing sheet to the lower side thereof.
According to other embodiments of the present invention, steps (b) and (d) each comprise cutting transversely through the circuit board substrate by means of a diamond table saw, and step (c) comprises cutting through the circuit board substrate longitudinally by means of a diamond wire saw, the separated segment of the circuit board substrate being maintained in a fixed position during the longitudinal cutting via a clamping device which grips the second portion of the circuit board substrate adjoining the first portion.
According to still other embodiments of the present invention, step (a) comprises providing the circuit board substrate as a laminate including a metal backing sheet adhesively bonded to the lower side of the circuit board substrate; steps (b) and (d) comprise cutting transversely through the thickness of the laminate; and step (c) comprises cutting the laminate longitudinally along the plane of the adhesive, the separated segment of the circuit board substrate being maintained in a fixed position during the longitudinal cutting via a clamping device which grips the second portion of the circuit board substrate adjoining the first portion.
According to yet other embodiments of the present invention, the method comprises the further step of: (e) electrically testing the IC device on the separated segment.
According to another aspect of the present invention, a method for reliable, safe removal of a die or chip comprising a semiconductor integrated circuit (IC) device from a fragile/brittle circuit board substrate comprises the sequential steps of:
(a) providing a laminate comprising a ceramic-based circuit board substrate having a planar upper surface with an IC die or chip mounted on a first portion thereof and a planar lower surface adhesively bonded to a metal support sheet, the IC device being electrically connected to the upper surface of the ceramic-based circuit board substrate via a plurality of very narrow diameter wires extending therefrom to a plurality of bonding pads formed on the first portion;
(b) cutting the laminate transversely through the thickness thereof to separate therefrom a segment comprising the first portion including the IC device and an adjoining second portion;
(c) cutting the separated segment longitudinally along the plane of the adhesive, parallel to the planar upper surface, the cutting extending beneath the entirety of the first portion; and
(d) cutting the laminate of the separated segment transversely through the thickness thereof to separate the first portion including the IC device from the second portion.
According to embodiments of the present invention, steps (b) and (d) each comprise cutting transversely through the thickness of the laminate by means of a diamond table saw; and step (c) comprises cutting the laminate longitudinally along the plane of the adhesive by means of a diamond wire saw, wherein the separated segment is maintained in a fixed position during the longitudinal cutting via a clamping device which grips the second portion of the laminate adjacent the first portion.
According to further embodiments of the present invention, the method comprises the further step (e) of electrically testing the IC device on the separated segment of the laminate.
Additional advantages and aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein embodiments of the present invention are shown and described, simply by way of illustration of the best mode contemplated for practicing the present invention. As will be described, the present invention is capable of other and different embodiments, and its several details are susceptible of modification in various obvious respects, all without departing from the spirit of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as limitative.